Logic of schedulable? method; typo

Thank you for the great book, I really enjoyed it from the first to the last page.

In the `schedulable?` method of chapter 7 I believe there is a logical flaw: the method fails to respect the lead days before already scheduled trips that might follow the queried time period.
Of course this has no relevance to the purpose of the example, but it bothered me a bit while reading the chapter.